Field of the Disclosure
The present disclosure relates to a display device, and more particularly, to an organic light emitting display and an apparatus for driving the same. Although the present disclosure has a wide scope of applications, it is particularly suitable for reducing the number of devices and the area for circuits of the organic light emitting display, thereby reducing the size of a bezel of the organic light emitting display.
Description of the Background
An active matrix type organic light emitting display includes a self-luminous organic light emitting diode (hereinafter, referred to as an “OLED”) and is advantageous in that a response speed is fast, light emitting efficiency and luminance are high, and a viewing angle is wide. The OLED includes an organic compound layer formed between an anode and a cathode. The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), an electron injection layer (EIL), or the like. When a driving voltage is applied to the anode and the cathode of the OLED, a hole having passed through the hole transport layer (HTL) and an electron having passed through the electron transport layer (ETL) move to the emission layer (EML) to form an exciton, and consequently the emission layer (EML) emits visible light.
An organic light emitting display may be driven by a duty driving method. To implement the duty driving method, a light emission control signal (hereinafter, referred to as an “EM signal”) should be applied to each of subpixels. The EM signal is generated as an alternating current signal alternating between an ON level defined as a light-on time of each of subpixels and an OFF level defined as a light-off time of each of subpixels, and light-on and light-off time of each of subpixels is referred to as a duty ratio of the EM signal. In a p-type metal oxide semiconductor field effect transistor (MOSFET), an ON level is a low logic level, and an OFF level is a high logic level.
To implement the duty driving method, an EM driver capable of switching the EM signal between the ON level and the OFF level at a desired time is required, and the EM driver includes a shift register for sequentially generating scan signals and an inverter for reversing the output of the shift register. Also, each subpixel has a pair of switch devices turned on or off by the EM signal, in which one switch device switches current supply of the OLED according to the EM signal, and the other switch device switches supply of reference voltage. Since the pair of switch devices is different in a turn-on time or a turn-off time, an additional EM signal should be provided, and accordingly a pair of EM drivers should be arranged for one subpixel. That is, for one subpixel, a pair of shift registers and a pair of inverters are arranged.
The EM driver may be formed in a bezel region of a display panel, and the bezel region is a non-display region arranged at the edges of the display panel. As described above, in the conventional organic light emitting display including a pair of EM drivers, since the circuit area of the EM driver is relatively large, the bezel region of the display panel inevitably becomes widened. Accordingly, it is difficult to implement a narrow bezel. Also, a layout space of the circuit is reduced, so that it is difficult to implement the circuit.